Keep unlogged-samples object for minidump.

base/metrics/histogram.cc

Index: base/metrics/histogram.cc
diff --git a/base/metrics/histogram.cc b/base/metrics/histogram.cc
index b7ef10749f86c7387f553137882474497801e311..1bfcffc0804009b71b70a1e06098f40b0551e577 100644
--- a/base/metrics/histogram.cc
+++ b/base/metrics/histogram.cc
@@ -614,12 +614,14 @@ std::unique_ptr<SampleVector> Histogram::SnapshotAllSamples() const {
 
 std::unique_ptr<SampleVector> Histogram::SnapshotUnloggedSamples() const {
   // TODO(bcwhite): Remove these CHECKs once crbug/734049 is resolved.
+  HistogramSamples* unlogged = unlogged_samples_.get();
   CHECK(unlogged_samples_);
   CHECK(unlogged_samples_->id());
   CHECK(bucket_ranges());
   std::unique_ptr<SampleVector> samples(
       new SampleVector(unlogged_samples_->id(), bucket_ranges()));
   samples->Add(*unlogged_samples_);
+  debug::Alias(&unlogged);
   return samples;
 }